1. Field of the Invention
The present invention relates to data processing apparatuses. More particularly, the present invention relates to a data processing apparatus that displays characters and images on a display device, such as, for example, a liquid crystal display device, an organic material display device, and the like.
2. Description of the Related Art
Conventionally, a data processing apparatus may include a hand-carry telephone (hereinafter, mobile phone), a hand-carry data terminal such as a Personal Digital Assistant (PDA), or the like. These are equipped with a liquid crystal display apparatus, an organic material display device, or the like, and an operation processing apparatus (corresponding to, for example, a host CPU in a mobile phone and a main processor in a PDA). Conventionally, when characters and images are displayed on a display device in a data processing apparatus, the operation processing apparatus in the data processing apparatus directly sends data to a display engine that drives the display device (corresponding to, for example, a liquid crystal driver IC when the display device is a liquid crystal display apparatus).
FIG. 6 shows the structure of part of a conventional mobile phone. Referring to FIG. 6, a mobile phone 50 includes a host CPU 51, a display engine 52 and a liquid crystal display device 53. The display engine 52 comprises a liquid crystal driver IC 54. The host CPU 51 and the liquid crystal driver IC 54 are connected by a host interface 55. The host interface 55 includes, for example, a chip select signal line, a read signal line, a write signal line, a data signal line, an interrupt signal line, and the like.
The conventional mobile phone shown in FIG. 6 is limited to displaying characters (such as alphanumeric messages) and still images, but cannot execute Personal Information Management (PIM) software, or handle video images. In contrast, third generation mobile phones (smart phones) that have been under development in recent years, and digital cameras, use high-speed signal processing apparatuses such as Digital Signal Processors (DSPs) as display engines so that a high data rate for transferring video images can be handled, and PIM can be executed.
FIG. 7 shows the structure of a part of a third generation mobile phone. Referring to FIG. 7, the third generation mobile phone 60 includes a host CPU 61, a display engine 62 and a liquid crystal display device 63. The display engine 62 comprises a high-speed signal processing apparatus 64 such as DSP, or the like, and a liquid crystal driver IC 65. The host CPU 61 and the high-speed signal processing apparatus 64 are connected by a high-speed bus interface 66. The high-speed bus interface 66 includes, for example, a chip select signal line, a read signal line, a write signal line, a data signal line, an interrupt signal line, and the like. Also, the high-speed signal processing apparatus 64 and the liquid crystal driver IC 65 are connected by a liquid crystal controller interface 67. The liquid crystal controller interface 67 includes, for example, a display data line that transfers display data or the like that has been subject to signal processing.
However, in order to adopt the conventional mobile phone shown in FIG. 6 to the third generation mobile phone 60, the host controller interface 55 of the conventional mobile phone, as viewed from the host CPU 51 to the display engine 52, needs to be substantially modified to function as the high-speed bus interface 66, as viewed from the host CPU 61 to the display engine 62.
Also, in the third generation mobile phone 60 shown in FIG. 7, the high-speed signal processing apparatus 64 needs to be always operated without regard to whether the mobile phone is being used for conversation or its PIM function is being used, and therefore its power consumption is large.